[FIX] stock: unreserve quants before assignment

Make sure to unreserve all quants before assignment. Indeed, the method
makes this assumption and does not take into account any existing
reserved quants. Therefore, without this fix, there is a possibility to
reserve more than needed.

opw-653904

addons/stock/stock.py

@@ -2345,6 +2345,7 @@ class stock_move(osv.osv):
         main_domain = {}
         todo_moves = []
         operations = set()
+        self.do_unreserve(cr, uid, [x.id for x in self.browse(cr, uid, ids, context=context) if x.reserved_quant_ids and x.state in ['confirmed', 'waiting', 'assigned']], context=context)
         for move in self.browse(cr, uid, ids, context=context):
             if move.state not in ('confirmed', 'waiting', 'assigned'):
                 continue